Reverts a14aa0d. The "skip when demand unchanged" optimisation broke
the live demo: in some real conditions (basin transitions, safety
controller activations) PS sends repeated demand=0 and the optimisation
correctly turned pumps off the first time but then declined to re-act
when conditions changed in a way the test suite didn't cover. Live
result: pumps stayed off even when basin filled to overflow.
The original symptom (pumps stuck mid-ramp under saturated demand) needs
a different approach — likely a pump-side guard rather than an MGC-side
demand filter. Investigating in a follow-up.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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